With respective developments of mobile communications technologies and broadband wireless access technologies, services of the mobile communications technologies and services of the broadband wireless access technologies permeate each other. In order to meet a broadband requirement of mobile communications and to response to a challenge of mobile broadband communications, technologies such as carrier aggregation (carrier aggregation, CA) are introduced into a mobile communications system.
With the CA technology, a wider bandwidth is obtained by aggregating multiple continuous or discontinuous component carriers, thereby improving a peak data rate and a system throughput and meanwhile solving a problem of a discontinuous operator spectrum. A user equipment (user equipment, UE) may support aggregation of multiple component carriers (component carrier, CC) in downlink and uplink. The aggregated multiple component carriers include a primary component carrier and at least one secondary component carrier. When the aggregated component carriers belong to different base stations, a technology of inter-base station CA (or referred as cross-base station CA) is involved. In the technology of inter-base station CA, a base station to which the primary component carrier belongs is a primary base station, and a base station to which a secondary component carrier belongs is a secondary base station. Specifically, both the primary base station and the secondary base station may be macro base stations or micro base stations (or referred as small base station). Certainly, the primary base station may be a macro base station, and the secondary base station may be a micro base station. In a scene where the macro base station is the primary base station and the micro base station is the secondary base station, the macro base station and the micro base station simultaneously serve the UE to improve throughput of the UE. Specifically, the macro base station may provide coverage and mobility management, and the micro base station may provide data transmission.
Presently, it is complicated to implement a protocol of the secondary base station. Even the secondary base station is a micro base station, it needs to implement a basic protocol stack and functions of a common base station, for example, all functions of radio link control (radio link control, RLC) and media access control (media access control, MAC); hence, cost of the micro base station is difficult to be reduced.